We are getting our Christmas tree and I am fretting about "my" decorations. I can see them in my mind, wrapped in tissue paper in a box in X's house. There are the white porcelain birds on red string, the paper origami stars, the gaudy glitterballs that the youngest loves: the whole collection is a sort of family history, a visual biography of our lives together. It belongs to all of us, but I'm the curator and I need at least some of them back.

I text X. "Can I come round and get some decorations?"

"K," he replies. It sounds terse, but when I go round, he is perfectly friendly. We go upstairs and he opens a couple of cupboards, vaguely. "My mum tidied up. It should all be there."

He wanders off, leaving me to rummage around. I eventually find a small subset of the decorations in a box I don't recognise, then some tinsel in a plastic bag, and finally another box, in another room. I feel irrationally cross. Why has X's mother taken it on herself to mess around with my decorations (yes, it's "my" now)? I put the boxes down on the table and start sorting.

X wanders in. "All all right? Got what you want?"

"I don't think everything's here."

"It should be," he says, puzzled.

"Well it's not."

"But," he says, with exaggerated reasonableness, "you weren't going to take everything anyway, were you?"

"No, I just wonder where the holly leaves and the dragonfly are." I sound a bit deranged, but this has taken on a disproportionate significance.

He shrugs. "No idea."

We go through the decorations I've found, until we've got about half each. With relief, I locate my very favourite: a miniature glass Christmas tree, with miniature glass ornaments. I love that thing. I leave him all the lights, the tinsel, the glitterballs and most of the big decorations, but I take the smaller, prettier things that I bought and love. My bad mood seems to affect him too, and we part quite tersely. I walk home feeling a combination of guilt and hurt.

I stop to buy fairy lights, and a couple of other bits and pieces, to make sure the tree isn't too bare. I go slightly overboard and buy a large plastic LED star that does, it turns out, a slightly nauseating colour change – purple to red to blue.

When the children get home from school, we head out to choose a tree from the morose man in a Santa hat, who is selling them on a patch of wasteland down the road. "Not too big," I warn. "I have to carry it." Also, they are eye-wateringly expensive. Sixty quid for a tree? They are not even gigantic, luxury trees, just ordinary, slightly misshapen ones.

"I can't carry that. How about this?" I point to a modest four-footer.

"Noooooo, it's tiny."

We finally find a compromise tree (short, but bushy) and carry it slowly, ceremonially, home. Ten minutes later, while we are decorating it, the youngest pulls out my mini glass tree and it shatters. His face sags with shock, but I can't pretend it's OK. I sweep up, crying into the dustpan, then sit on a stool in the kitchen with my head in my hands and cry some more. Finally, I blow my nose and go back into the living room. The children have retreated to the sofa, silently watching TV with the sound turned down.

I sit between them, and shuffle the youngest onto my knee. "It doesn't matter, accidents happen," I say, squeezing him tightly, and we watch Sponge Bob for a while.

Later, we finish the tree. It looks brilliantly bonkers: shabby, over the top, bathed in purple and red light from the plastic star. "It's fabulous," I tell the boys. "Now it's properly Christmas!"